This invention relates to a chisel system and, more particularly, to an improved modular chisel system for cutting an opening to receive an implant in an osteochondral implant procedure.
In the human body, the knee consists of three articulating components—a femur, a tibia, and a patella—that are held in place by various ligaments. The corresponding chondral areas of the femur and the tibia form a hinge joint, and the patella protects the joint. Portions of the latter areas, as well as the underside of the patella, are covered with an articular cartilage, which allow the femur and the tibia to smoothly glide against each other without causing damage.
The articular cartilage often tears, usually due to traumatic injury (often seen in athletics) and degenerative processes (seen in older patients). This tearing does not heal well due to the lack of nerves, blood vessels and lymphatic systems; and the resultant knee pain, swelling, and limited motion of the bone(s) must be addressed.
Damaged adult cartilages have historically been treated by a variety of surgical interventions including lavage, arthroscopic debridement, and repair stimulation, all of which provide less than optimum results.
Another known treatment involves removal and replacement of the damaged cartilage with a prosthetic device. However, the known artificial prostheses have largely been unsuccessful since they are deficient in the elastic, and therefore in the shock-absorbing, properties characteristic of the cartilage. Moreover, the known artificial devices have not proven able to withstand the forces inherent to routine knee joint function.
In an attempt to overcome the problems associated with the above techniques, osteochondral transplantation, also known as “mosaicplasty” or “OATS” has been used to repair articular cartilages. This procedure involves removing injured tissue from the articular defect and drilling cylindrical openings in the base of the defect and underlying bone. Cylindrical plugs or grafts, consisting of healthy cartilage overlying bone, are usually obtained by using a chisel to punch them out from another area of the patient, typically from a lower load-bearing region of the joint under repair, or from a donor patient. The harvested grafts are then implanted in the openings.
In these cases, the chisels used to harvest the grafts are, for the most part, one-piece designs that consist essentially of a blade portion extending from a handle portion. Thus, once the grafts are harvested, they remain in the hollow, distal end portion of the chisel and must be removed from that end. This often causes damage to the graft, and in most cases to the cartilage portion of the graft.
Also, the cutting end of the chisels are blunt and thus can cause damage, in the form of high mechanical deformation, as the cartilage portion of the graft is punched out during the harvesting procedure. Further, each chisel can cut only one size graft, which requires a series of chisels for cutting a series of grafts having different dimensions. However, to provide a separate chisel for each size graft is expensive.
Therefore what is needed is a chisel system that overcomes the above problems.